The invention relates to communicating with devices positioned outside a liner in a wellbore.
Oil and gas wells may be completed with a variety of downhole devices to produce hydrocarbons from, or inject fluids into, formations beneath the earth surface. Completion equipment have been developed for many types of wells, including vertical or near-vertical, horizontal, deviated, and multilateral wells. Typical completion equipment include valves, tubing, packers, and other downhole devices, as well as electrical, optical, or hydraulic devices to monitor downhole conditions and to control actuation of downhole devices (e.g., opening or closing valves, setting packers, and so forth).
Sensors and control devices may also be mounted on or positioned outside of a liner, which is typically cemented to the wall of the wellbore. A special type of liner includes casing, which is a liner that extends to the well surface. A liner may also be connected below a casing to extend further into the wellbore or into a lateral branch of a multilateral well. One type of sensor that may be mounted on the outside of a casing includes resistivity electrodes, which are used to monitor the resistivity of a surrounding formation reservoir. Based on the resistivity information, various characteristics of the formation may be determined.
A conventional technique of communicating with the sensors mounted on the outside of casing includes running a control line outside the casing to the well surface. However, running one or more control lines in the cement layer creates a potential leak path to the well surface, which is undesirable. In addition, for liners that do not extend to the well surface, use of this technique may not be available. Another drawback of running a control line on the outside of the casing is that the control line may have to cross wellhead equipment at a relatively inconvenient location.
A need thus exists for a mechanism to provide communication with downhole sensors or control devices that are positioned outside of liners in a wellbore.